The aim of this project is to elucidate new patterns of structure in nucleic acids and to determine the sterochemistry of nucleic acid- protein interactions using the methods of x-ray and neutron crystallography. Conformations of helical nucleic acids are understood; however, the conformations within loops, such as found in t-RNA have not, as yet, been clarified. Studies on oligonucleotides will therefore be continued. Nucleic acids and proteins coexist in, for example, chromosomes, viruses and ribosomes. By studying the structures of small model compounds such as base-amino acids and nucleoside peptides, one can take advantage of non covalent interactions which occur between molecules in crystals to begin a characterization of the various interactions among nucleic acid and protein components. Furthermore, some of the compounds used for this study have either anti-viral activity or are radiation products. Thus, insight may be gained into the mechanism of action of some chemotherapeutic agents as well as the action of ionizing radiation on biological materials.